Polymeric compositions and their method of manufacture



' mers, terpolymers.

United States Patent Patented May 9, 1961 POLYMERIC COL [POSITIONS ANDTHEIR METHOD OF MANUFACTURE No Drawing. Filed Jan. 7, 1959, Ser. No.785,318 22 Claims. (Cl. 260-23) This invention relates to thepreparation of new polymeric products, particularly shaped structuresand coatings of polymers obtained from aliphatic l-olefins with vinylesters. One object is to provide a novel process for preparing aliphaticl-olefin/vinyl ester polymeric compositions. Another object is toprovide novel three-component poly- A further object is to providefibers and films and other Other objects will appear hereinafter.

.In its broadest terms,'the present invention involves hydrolyzing,either partially or completely, a polymer obtained from an aliphaticl-olefin such as ethylene and a low vinyl ester of a monocarboxyl-icacid such as vinyl formate, vinyl acetate, vinyl propionate, and thelike; then re-es-terifying, usually with an esterifying agent of asubstantially higher molecular weight ester'group; and thereafter, ifdesired, convert the polymer into films, fibers or the like.

This method provides a novel route tootherwise difficultto obtainaliphatic l-olefin/vinyl ester copolymers such as ethylene/vinylsalicylate, ethylene/vinyl laurate, etc. But even more important, thismethod provides a route to substantially line'ar terpolymers ofaliphatic 1- olefin/low'vinyl ester/high vinyl ester, the undesirablebranching beingvirtually eliminated by the process of the presentinvention.

Preferably, the invention comprises copolymerizing n moles, n being aninteger, of a vinyl ester having the structural formula wherein R is anacyl radical derived from an organic monocarboxylic acid, said acylradical having x carbon atoms, x being an integer having a value of atleast one, preferably 1-7, with at least 222 moles of an aliphaticl-olefin, preferably ethylene; hydrolyzing the resulting copolymer-toremove y ester groups, y being an integer having a value of from n/20 ton, preferably no more than 2n/3; and esterifying the hydrolyzed productwith y esterifying groups selected from the group consisting of acylradicals derived from organic monocarboxylic acids having at least (x+l)carbon atoms (preferably 11-24 carbon atoms) and acyl radicals of theformula -CR' wherein R is hydroxy-aryl.

The resulting terpolymers tend to be inherently per manentlyplasticized. Plasticization is attributed to the higher molecularweight, particularly of the long chain ester groups added in the finalesterification step. The

shaped structures of these polymers. I

droxy-aryl containing acyl groups such as the salicyl group for aportion of the low molecular weight acyl groups tends to add theproperty of light stability to the improved characteristics of theethylene/vinyl ester terpolymer.

' The invention will be described for use in the production ofself-supporting films and sheets for wrapping purposes and the like.However, it should be understood that the invention is applicable to thepreparation of shaped structures of all types and to the preparation ofcoatings. Thus, it is contemplated that the polymeric compositions ofthe present invention will find use as filaments, films, rods, tubes,laminates, adhesive and nonadhesive coatings, etc.

The process of the invention involves a combination of three steps, eachof which is absolutely essential in achieving the final result. In thefollowing sections of the'specification, each of the three steps,copolymerization, hydrolysis and re-esterification, are discussedseparately.

COPOLYM'ERIZATION In the first step of the process an aliphatic l-olefinsuch as ethylene, propylene, butene-l, isobutylene, pentene-l andhexene-l is copolymerized with a vinyl ester derived from a lowsaturated fatty acid. The vinyl ester is preferably vinyl acetate orvinyl formate but obviously any available relatively low molecularweight vinyl ester, preferably no higher than vinyl enanthate, may beused.

Copolymerization may be performed by any method known to the art. Forexample, to prepare an ethylene/vinyl acetate copolymer, ethylene may bereacted under pressure in an emulsion process with vinyl acetate in thepresence of a reduction-oxidation catalyst. The resulting copolymer, inthe form of a latex, may be coagulated with a brine solution; the brineis removed by washing with water and the copolymer is then dried. Such aprocess is disclosed more fully in US. Patent 2,703,794 to M. J. Roedel.The process involves essentially polymerizing the aliphatic l-olefin andthe vinyl ester in the presence of a reducing agent and an oxidizingagent, the agents being capable of generating a free radical by areduction-oxidation reaction.

The preferred ratio of the aliphatic l-olefin (ethylene) to the vinylester (vinyl acetate) is at least 2 to l but may be as high as 50 to 1and as low as l to 5. The degree of polymerization in the copolymershould be at least 100 as defined by Staudinger in Die Hoch MolekularenOrganischen Verbindungen (1932).

HYDROLYSIS The term hydrolysis is intended to include alcoholysis aswell as hydrolysis with water. This step is preferably carried out bydissolving the copolymer in a primary alcohol which is liquid at 25 C.or in an alcohol-toluene solvent mixture composed of at least 25% byweight of the alcohol or in an aromatic hydrocarbon solvent such astoluene and then treating agent or catalyst.

The most suitable alcohols are methylalcohol and ethyl alcohol, buthigher alcohols such as propyl, butyl and isobutyl alcohol may also beused to advantage. In cases where the sufficiently soluble in thealcohol, a mixed solvent or an aromatic hydrocarbon solvent may be usedto improve solubility. Thus, the alcohol may be used in a mixture withbenzene, toluene, xylene, pyridine, dioxane, trichloroethylene,cyclohexane, "n-heptane or the like. cases, hydrolysis may be carriedout in solvent with a suitable hydrolyzing other water-misciblesolvents.

olefin/vinyl ester copolymer is not In some 3 systems containing water;for example,"water with acetic acid or with dioxane or with ethanol orwith methanol or Thehydrolyzing catalyst-is preferably an alkalicatalyst that operates either by straight saponification or as anester-interchange or alcoholysis catalyst. Sodium hydroxide'isavailable, cheap-and, therefore, preferred. I-ldwever, other{alkalinematerials such as 'thehyd'r'oxidesiof potassium, lithium, rubidium,'c'alciiim, strontium, barium mayalso be used. rnsome instances, notpreferred but where a slower rate of hydrolysis is desired, an acidcatalyst such as sulfuric acid, phosphoric acid,-p-to1uenesu-lfonicacid, hydrochloric acid andthe like may be used.

With the alkali catalyst the reaction is usually carried out -at'anelevated terriperature, i.'e., at the boiling point ofthe solvent, andis complete in less than one hour. The eiit'eritof hydrolysis iscontrolled by the amountof alkali catalyst employed. I I g The result ofthehydr'olysis step may be a completely hydrolyzed product or apartially hydrolyzed product.

The "completely hydrolyzed products will obviously be the sar'neregardless of the vinyl ester 'in the original co polymer. The partiallyhydrolyzed products will contain in the polymer chains CH(OH) groups 'aswell as CHOR groups (where R is an acyl radical of a mono: carboxylicorganic acid) and methylene groups. However, in the preferred hydrolysisproduct more than half of the groups will be methylene groups and theratio of CHOR groups-to CH(OH) groups will range from 1.2

to 20:1. I

ESTERI'FICATION The purpose of the esterification step is to convert theCH( OH) groups to CHOR groups wherein R is either an acyl radical of along chain monocarboxylic-acid (having more carbon atoms than the Rradical), preferably a fatty acid having at least 11 carbon atoms, or anacyl radical of a hydrdxy-aryl acid.

After isolating the completely or partially hydrolyzed ethylene/vinylester, the est'erification agent is added to the polymer, the polymerbeing in an organic solvent such as toluene, benzene, xylene, pyridine,dioxane, trichloroethylene, cyclohexane, n-hept'ane, etc. Isolation ismost easily accomplished by azeotr'opic distillation of the excessalcohol-water-added by the previous hydrolysis step. This distillationleaves the polymer in the desired solvent. However, if desired, thepolymer may be filtered and washed and new solvent added prior to theaddition or the esterification agent.

The e'sterifica'tioh agents which may be the halides, anhyd'rides, orthe acids themselves containing the R acyl radical are added to thehydrolyzedproduct in the solvent usually under anhydrous conditions. Themixture is then refluxed fora period which may be from minutesfto 24hours or more. The-'re e'st'eIified product is then filtered and washedwith alcohol to remove excess esterification agent.

Among the esterifying agents which may be used are ac'etyl chloride,propionyl chloride, n-butyral chloride, nvaleryl chloride, isovalerylchloride, n-caproyl chloride, n-caprylyl chloride, n-capryl chloride,n-lauroyl chloride, n-myristoyl chloride, n-palmityl chloride,n-stear-yl chloride, or the bromides and iodidesof these compounds,n-caproic anhydrides, n cap'rylic anhydride, n-capryl anhydride,n-lauric anhydride, n-myristic anhydride, n palrnitic anhydride,n-stearic anhydrid'e, salicylyl chloride, salicyclic acid, meta-orpara-hydroxy benzoic acid. When re esterifying with higher aliphaticcarboxylic radicals, a practical upper limit of chain length is analiphatic carboxylic acid of about 24 carbon atoms.

The resulting copolymers or terpolymers maybe used directly in theformation of film, fibers and the like by processes well known to thoseskilled in the art. The polymers can be molded into objects, extruded astubing, filaments, films, rods, etc. and melt cast or cast from suitablesolvents to provide thin films and the like. Solutions of thepolymersmay be *coatedon paper, fabrics, or on films of other polymericmaterials s'uchas regening the best mode contemplated 'fdr performing therated cellulose films to impart desirable properties to the thus coatedbase films.

The polymers may also be modified prior to or subsequent to shaping. Themodifying agents may be selected from a variety of types such aspigments, waxes, inorganic and organic fillers, etc. One particularlydesirable modification involves reaction with siliceous particles asdescribed in, 'UgS. patent application Serial No. 602,398 to Richard D.Pruett, filed August 6, 1956. The result or such modification with'siliceousparticle's in medianner disclosed by the aforementioned patentapplication is to increase the tear strength and tenacity of thepolymer, while "avoiding the increase -in stiffness or tensilern'odu'lus that is obtained when the ethylene/low molecular weight vinylester copolyn'iers are similarly rno'dified.

The invention will be more clearly understood by referring to thefollowing examples, Example I represente nven- These examples,illustrating specific odiments tion.

of the present invention, should not be considered liiriitative.

Example I An ethylene/ vinyl acetate copolymer (4/1 mole ratio) wasprepared by adding the following to a one-liter stainless steel rockertubeundera stream of nitrogen: asolution of 3 grams Nag-IP0 and 10 gramsof Duponol ME 1 in 280 mls. of deoxygenated water, a solution 'of 0.14gram of-FeSQ 7H- 0:and 0.23 gram of Na P O -l0H O, 054 grain of K S O0.21 gram of NaHSO and mls. of vinyl acetate. The rocker tube wasevacuated and pressured to 400 atmospheres with ethylene containing lessthan 10 parts per million of'oxygem The rocker was started and thetemperature brought to-30 C. for a '2 hour reaction period. At the endof'this time the rocker contents were discharged in the form of a'latex,'the -lat'ex was coagulated with brine, washed with waterand'dried. A yield of 40 grams of copolymer was obtained. Infraredanalysis showed the copolymer to contain approximately 4 moles ofcrnnbined ethylene per'r'niole'o f coinbined vinyl acetate.

Twenty grams of the copolymer was dissolvedfin 200 mls. of toluene withstirring. A's'olution "or ).4 'gra'i'n of sodium hydroxide in 20 mls. ofmethanol and Qinlsz'of water was added drop-wise to the 'copolyni'e'rsolnt-ion. The excess methanol and "water was then azeotropic'allydistilled from the solution until the temperature in "the vapors reachedC.

Fifteen grams of n-stearyl chloride was then added to the toluenesolution of the partially hydrolyzed polymer in the reaction flask.Thefniixture then refliixedii't a temperature of 1 10 C. for two hoursThe rest} rig product weighing {21 rams was precipitated, filtered andwashed with methanol. -By infrared absorption analysis, it wasdetermined that "the product was a flteifpolyine r 16f ethylene/vinylacetate/vinyl stearate ('80/18/2 aisle ratio)- r. v

The polymer as'presse d into a film by pressing in "a Carver :press atllO C. for one minute at 3 0 tons p'r'essure The resulting film, .005thick, was flexible and displayed substantially no tackines's, evenafter agingfo'r 90 days. 7

Example 11 1. The sodium salt 0t sulfated lau'rylalcohol, manufactured.

by'E. I. duPont de Nemours & C0.

resultantslurry was poured into a suction funnel, washed with warm waterto remove all soluble salts, then dried in a vacuum oven at 50 C. Theproduct was 48 grams of a white powder, the partially hydrolyzedethylene/vinyl acetate polymer.

Twenty-four grams of the hydrolyzed polymer was then esterified by firstadding 200m1s. of toluene and then 11 grams ofn-lauroyl chloridefollowed by refluxing at atemperature of 110 C. for two hours. Theresulting product weighing 24 grams was precipitated, filtered andwashed with methanol. By infrared absorption analysis, it was determinedthat the product was a terpolymer of ethylene/vinyl acetate/vinyllauroate (80/ 18/2 mole ratio).

The polymer was pressed into a satisfactory flexible film by pressing ina Carver press at 30 tons pressure for one minute at 110 C. a 1

Example III product was isolated by precipitating and washing withmethanol. By infrared absorption analysis, it was de+ termined that theproduct was a terpolymer of ethylene/- vinyl acetate/vinyl caproate(80/18/2 mole ratio).

The polymer exhibited adhesive properties adaptable for use in apressure-sensitive adhesive.

Example IV The procedure of Example I was again repeated using 20 gramsof the ethylene/vinyl acetate copolymer (4/1 mole ratio) dissolved in200 mls. of toluene. A solution of 0.4 gram of sodium hydroxide in 20mls.-of methanol and 4 mls. of water was added drop-wise to thecopolymer solution.

After azeotropically distilling the excess methanol and water, 3 gramsof salicylic acid and 0.2 gram of p-tolu- -ene-sulfonic acid were addedto the solution of the par;

tially hydrolyzed polymer. The mixturewas refluxed for 24 hours under ablanket of nitrogen ata temperature of 110 C. using a Dean-Stark waterseparator trap. The product was isolated by precipitating and washingwith methanol. By infrared absorption analysis, it was determined thatthe product was a terpolymer of ethylene/ vinyl acetate/vinyl'salicylate(80/ 18/2 mole ratio).

The polymer was formed into a satisfactory film by the proceduredescribed in Example 1.

Example V The procedure of Example II was repeated to prepare 24 gramsof the partially hydrolyzed ethylene/vinyl acetate copolymer in 250 mls.of toluene.

The polymer solution wastreated with 5 grams of propionyl chloride andheated at 70 C. with stirring for three hours. The product weighing 23.8grams was isolated by precipitating and washing with methanol. Byinfrared absorption analysis, it was determined that a terpolymer hadbeen obtained, a terpolymer of ethylene/ vinyl acetate/vinyl propionate(80/18/2 mole ratio).

The resulting terpolymer was milled with 8.0 grams of Cab-.O- Sil 1siliceous particles in a rubber mill at 120 130- C. for 15 minutes andwas then pressed into a film in aCarver press heated at 120 C. for oneminute at 30 tons pressure. The resulting modified polymeric filmProduct; manufactured by Godfrey L. Cabot, Inc.

had a low tensile modulus, an increased tear strength while thesatisfactory tenacity level of the unmodified terpolymer product hadbeen retained.

Example VI A 14/1 mole ratio ethylene/vinyl acetate copolymer wasprepared by adding the following to a one liter stainless steel rockertube at 0 C. under a stream of nitrogen: a solution of 220 mls. ofdeoxygenated water containing 10 grams Duponol ME, 20 mls. ofdeoxygenated water containing 0.14 gram of FeSO -7H O and 0.23 gram ofNa P O -l0H O, mils, deoxidized tertiary butyl alcohol, 0.31 gram ofl-ascorbic acid, 0.26 gram of cyclohexanone peroxide and 50 mls. ofvinyl acetate. The rocker tube was then evacuated and pressured to 400atmospheres with ethylene. The rocker was started, the temperature wasbrought to 30C. and the pressure to 1000 atmospheres for a two hourperiod. There was obtained 40 grams of copolymer. I

Fifteen grams of the copolymer was dissolved in 150 mls. of boilingtoluene. After the copolymer solution was cooled to about 50 C., 1.24grams of sodium hydroxide dissolved in 25 mls. of a 98% methanol/2%water mixture was added slowly with stirring. After stirring for 30minutes while maintaining the temperature of the mixture at C., excessmethanol and water was *azeotropically distilled from the solution untilthe temper:

a-ture of the vapors reached C. The resultant slurry was poured into asuction funnel, washed with warm water to remove all soluble salts, thendried in a vacuum oven at 50 C.

Twelve grams of the completely hydrolyzed polymer was then dissolved inmls. of toluene. About ten grams of salicylyl chloride was then. addedslowly to the solution and the mixture was refluxed at a temperature of110 C. for 1% hours. The resultingproduct was precipitated, filtered andwashed with methanol. By infrared absorption analysis, it was determinedthat a substantially quantitative yield of the copolymer of ethylene/vinyl salicylate (14/1 mole ratio) had been obtained.

A portion of the polymer was then pressed into a film by heating in aCarver press at 110 C. for one minute under 30 tons presure. The filmdisplayed improved stability toward the degrading effect of light asshown by the following test: Strips of thefilm were attached to a frameand then exposed to the light of four 20-watt fluorescent sun lamps(Westinghouse No. FS20T12) in a box, the distance of the strips from thelamps being 2%. A reflector was prqvided'behindeach lamp. -Eachstrip.was manually tested for tear-resistance and flexibility. Theethylene/vinyl salicylate film of this, example remained flexible andretained good tear strength at 750 hours whereas a polyethylene controlfilm had badly impaired tear strength and reduced flexibility at 300hours.

Having fully disclosed the invention, what is claimed. is:

1. A process which comprises the steps in sequence of copolymerizing avinyl ester having the structural formula place y ester groups with yhydroxyl groups, y being an integer; and re-esterifying the hydrolyzedproduct with y ester groups selected from the group consisting of acylradicals derived from organic monocarboxylic acids, said reases an?)radicals having atieastx+1cabon atom and acyl radicals of the formulawherein R is hydroxyl-a'ryl.

2. A process which comprises the steps in sequence of copolymerizing nmoles "of a vinyl'esteihaving the structural'formula oH,=oo-n wherein "Ris an acyl radical derived from an organic monocarboxylic acid, said'acylra'dica'l having carbon atoms, x being an {integer having-a valueor at least 1, withat least 271 moles Oran aliphatic l-olefin to form avinyl e'sterlali'ph'atic l-olefin copolyn'ier hydrolyzi'ng saidcopolynier to replace y ester groups with y hydroiiy-l groups, y beingan integer from n/ 20 ton; and re-ester' ifyingthe hydrolyzed -productwith y 'e'ster groups selected from the group consisting-of acylradicals derived from organic monocarboxylie acids, said 'acyl radicalshaving at least x+1 carbonatoms and acyl radicals of the formula 2g;-*-C-R' w erein R' is hy'droxy aryl.

3. A process which comprises the steps in sequence of copolymerizing 'nmoles of a vinyl ester having the structural formula 3 CH5CO'R whereinis an acyl radicaljde'rived from "an organic monocarboxylic acid, saidacyl radical having x carbon atoms, x being an integer having a'v'alueiof a least 1, with at least 2n moles of an aliphatic lbl'e'finfto fo'rr'nfa vinyl ester/ aliphatic l-oleiin copolymer;hydrolyzi'ngs'aid copolymer to replace y ester groups with y hy'dro'iiylgroups, y being an integer fro'rn it/29th 2n'/-3; and-reeste'rifyin'gthe hydrolyzed product with y ,este'r groups selected from the groupconsisting of acyl radicals derived from organic monocarboxylicacids,'*said 'acyl radicals having at least x'+l carbon atoms and ac'ylradicals of the formula *i -(JJR.

whereiniR i; hyarexy-a'ryl. I

process which eempfis'es tlie steps in s'eq of 'copoly'merizing it molesof 'a vinyl'ester lzia iiig the structural formula i om=o-o-1t wherein Ris "an acyl radical derived froiii *an organic monocarboxylic acid, saidacyl radical having 1-7 carbon atoms with at least 2n moles of analiphatic l-olefin to form a vinyl ester/ aliphatic l-olefin copolyme'r;hydrolyzing said copolymer to replace y ester groups with y hydroxylgroups, y being an integer from n/20 to n; and reesterifying thehydrolyzed product with y ester groups selected from the groupconsisting of acyl radicals derived from fatty acids, said acyl radicalshaving at 'least 11 -24 carbon atoiiisandacyl radic'als of the formula Y1 wherein said aliphatic 6. Aprocess as in claim 1 wherein said vinylester in the copolymerizing step is vinyl acetate,

V g V 7-. A,proee's s which comprises thesteps in sequence ofcopolymerizing n moles of a vinyl ester having the structural formula ir wherein R is an acyl radical derived from an organic monocarboxylicacid, said acyl radical having x carbon atoms, -x being an integerhaving a value of at least 1, with at least 2n moles of an aliphaticl-olefin; dissolving the copolymer in a suitable solvent containing atleast 25% of a primary alcohol; adding an alkali catalyst to thesolution and heating to replace y ester groups with y hydroxyl groups, ybeing an integer from n/ZO to it; isolating the hydrolyzed product;adding an 'esteri'fyiing agent selected from the group consisting 'ofha'lides, an hydrides and acids containing an acyl radical, said acylradical being derived from'acids'selected from the group consisting :offatty acids having -x+l carbon atoms :and hydroxy-aryl acids to replacethe y hydroxyl groups.

'8. A process which comprises the steps insequence or copolymerizingethylene and vinyl acetate to format copolymer in-:which the mole ratioof ethylene to vinyl acetate is at least 2 to l; dissolving said polymerin =tolu- (am; adding a solution of sodium hydroxide in methanol andwater, the methanol comprising -95% of the mixture'of'iriethanol andwater; and heating to replace from "l0 all of the acetate groups withhydroxyl groups; isolating the'hydrolyzedproduct; adding an acylchloride, the "acyl "radical being derived from acids selected from thegroup consisting of fatty acids having 1'124 carbon atoms a-nd salicylicacid, and heating to :a temperature of 60 C. 9. A substantially 'linearterpolymcr of an aliphatic l-olefin; a vinyl ester having the structuralformula i I CHi=C-OR wherein R is acyl "radical derived from an organicmonocarboii'ylic acid, said acid having x carbon atoms, at being aninteger having a value of at least '1; and a vinyl ester having thestructural formula o-H1:i1-oit' wherein R" is an acyl radical selectedfrom the group consisting "of acyl radicals derived from fatty acidshaving x+ 1 carbon atoms and acyl radicals derived from a hydroxy-aryl'a'cid, saidter'polymer made by the process of claim 1. U

10. A suhstaritiallylinear terploymer of ethylene, vinyi acetate 'andavinyl ester "of a monocarboxylic acids'elected fi'or'n the vgroupconsisting of fatty acids having 11-24 carbon atoms and "salicylic acidmade by "the process of claim 4.

11. A substantially linear terpolymer of ethylene, vinyl acetate andvinyl stearate made by the process of claim 4.

'12. A s'ubstantiallyline'ar terpo'lymer of ethylene, :vinyl acetate andvinyl ca'p'roate made by the process of claim 4.

13L -A-suhs'tant-ia-lly linear terpolymer of ethylene, vinyl acetate andVinyl -salicylate made by the process of claim t. I

14. Asub'stantially linear terpolymerfofiethylene, vinyl acetate and*vinyl propionate made by the process of claim '4.

15. "A "shaped "structure comprising claim 9. a

16. A shaped structurecomprising the terpolyrner of c1aim 10.

17. 'A selfsupporting film comprising the :terpolymer of claim 9. a

18. A self-supporting film comprising the-terpolymer of claim 10.

the terpolymer or 19. A plasticized composition comprising theterpolymer of claim 9.

20. A plasticized composition comprising the terpolymer of claim 10.

21. A polymer prepared by the process of claim 2 "having the formulawherein n is an integer;

R is an acyl radical derived from an organic monocarboxylic saturatedacid having 1-7 carbon atoms; and

R" is an acyl radical selected from the group consisting of acylradicals derived from organic monocarboxylic saturated acids having11-24 carbon atoms and acyl radicals derived from hydroxy-aryl acids.

.10. 22. A polymer prepared by the process of claim 3 having the formula2 4)at least 211( 2 3 )n-(n/20 to zn/s) z a ")n/2o so all wherein n isan integer;

R is an acyl radical derived from an organic monoearboxylic saturatedacid having 1-7 carbon atoms; and

R is an acyl radical selected from the group consisting of acyl radicalsderived from organic monocarboxylic saturated acids having 11-24 carbonatoms and acyl radicals derived from hydroxy-aryl acids.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS WHICH COMPRISES THE STEPS IN SEQUENCE OF COPOLYMERIZING AVINYL ESTER HAVING THE STRUCTURAL FORMULA